One of the objectives of this research is to develop an understanding of the mechanisms by which teratogenic drugs such as hadacidin cause clefts of the secondary palate. Since the results of our previous research efforts showed that the eukaryotic microorganism Dictyostelium discoideum can be used as a model system for drug studies, the present proposal describes experiments using these cells as well as those of the palatal shelf as studied in organ culture. As part of this study we plan to study the mechanisms by which hadacidin retards morphogenesis and how, after aggregation, the cells overcome the effects of the drug. We plan to use (C14) hadacidin to monitor not only the uptake of the drug during morphogenesis but also its metabolic fate. Since the drug is labeled in a group susceptible to oxidation and decarboxylation, we should be able to determine if detoxification proceeds by the reactions of this type by measuring amount of radioactive CO2 released. The effect of hadacidin on the secretion of lysosomal enzymatic activities will also be studied. In particular, both glycosidase and protease activities will be followed using methods previously developed in this laboratory. Using radioactive fucose, a nutrient whose uptake we showed is uneffected by hadacidin, the biosynthesis of cell-surface glycoproteins and glycolipids can be followed and the effects of the drug on these pathways determined. A study on the effect of hadacidin on cAMP levels and the correlation between these values and morphogenesis is planned. Extensive studies are also planned on the question of detoxification of hadacidin by palatal tissue. Again (C14) hadacidin will be used and the release of CO2 measured. Also as part of this proposal we plan to study the effect of hadacidin on secretion of lysosomal activities and the formation of cAMP in palatal shelves.